Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In some situations, it is desirable for patients to be able to administer drugs and medicament by themselves, e.g., without the need for trained medical staff to administer the drugs. There are a number of different existing delivery devices with varying degrees of automatic functions. For instance, existing automatic injection devices provide a means for automatically propelling a plunger forward to eject medicament from the automatic injection device in response to activation of the device.
In existing devices, the means for automatically propelling the plunger forward to eject the medicament are often complex and expensive to manufacture. There is, therefore, a desire to reduce the cost of manufacturing automatic injection devices while maintaining the reliability of the injection device to eject the dose of medicament.
Further, for some types of medicaments, there is a desire to eject the medicament at a substantially constant force. However, certain existing devices for ejecting the medicament at a substantially constant force are complex and expensive to manufacture. There is a desire to reduce the cost of manufacturing automatic injection devices while maintaining the reliability of the injection device to eject the medicament at a substantially constant force.